Interstitial lung disease - a combination of pulmonary inflammation and fibrosis - remains the main cause of death in patients with systemic sclerosis, or scleroderma. The mechanisms of scleroderma lung disease (SLD) are not well understood, and the efficiency of available therapies is limited. Previous studies by us and others have suggested that the levels of a splice variant of Interleukin(IL)-4, so-called IL-442, are elevated in association with poorer outcomes in patients with SLD. Our new Preliminary Data suggest that acute adenovirus-mediated gene delivery of mouse (m) IL-442 to mouse lung in vivo recapitulates important features of human SLD, causing infiltration of lymphocytes, disturbances in cytokine milieu, and a tendency to collagen accumulation. The changes caused by mIL-442 in the acute gene delivery model are different from those caused by mIL-4, including the effects on gene expression, pulmonary cytokine milieu, and cellular infiltration. For example, while causing the mentioned changes resembling of human SLD, mIL-442 does not induce pulmonary eosinophilia or goblet cell hyperplasia (the features that are common in asthma but not in SLD, and that are readily induced by wild-type mIL-4). Based on these observations, we hypothesize that IL-442 may play a key role in SLD, and that targeting of IL-442 in patients with SLD may prove therapeutic. Considering that SLD in humans is a chronic condition, there is a need to assess molecular, cellular, and histological changes caused by chronic IL-442 expression in the lungs. We propose, in Specific Aim 1, to establish and investigate a chronic model of mIL-442 expression utilizing lentivirus-mediated gene delivery. In contrast to the adenovirus-mediated system, which allows only for a short-term gene delivery, the lentiviral system allows for gene delivery lasting for months, up to a life-long expression. The experiments will determine whether chronic expression of mIL-442 in an animal model recapitulates key features of scleroderma lung disease, including lymphocytic inflammation (particularly CD8+ T cells), fibrosis, changes in pulmonary cytokine milieu and expression of cell surface molecules, and resistance to treatment with corticosteroids and other immunosuppressive agents. These experiments will also identify key secondary mediators induced by mIL-442, and determine whether IL-442 promotes inflammation and collagen deposition by directly acting on the lung, or indirectly, by inducing expression of cytokines and cell surface molecules. Specific Aim 2 will identify, through pre- clinical testing, effective means of targeting human (h) IL-442. Specifically, the experiments will assess the efficacy of hIL-442-blocking monoclonal antibodies, and blockade of human IL-442 production through RNA interference. These experiments will form basis for future clinical trials targeting IL-442 in humans. The anticipated outcomes of this research are 1) better understanding of the mechanistic role of IL-442, and 2) pre-clinical development or a novel therapy for SLD. The results are likely to be beneficial for not only patients with scleroderma, but also patients with asthma, sepsis, and tuberculosis, in all of which IL-442 has been suggested to play a significant role.